1. Field
This disclosure relates to a thermosetting resin, a thermosetting resin composition, and a printed circuit board fabricated using the same.
2. Description of the Related Art
Various electronic devices such as computers, semiconductor devices, displays, and communication devices include printed electronic circuit boards. A printed electronic circuit board may include signal lines for transferring signals, insulating layers for preventing a short circuit between signal lines, switching elements, and the like.
The printed electronic circuit board may desirably have various performance factors to provide improved performance. For example, a printed electronic circuit may be formed as a thin film to improve the performance of an electronic device, and the printed electronic circuit may be very small in size.
Particularly, a board such as a copper foil laminate having a low-dielectric characteristic and a low-dielectric loss tangent characteristic is desirable in order to reduce loss of information and signal delay. Generally, signal delay in a flexible printed circuit (“FPC”) is increased in proportion to the square root of a relative dielectric constant of an insulation material around the wire, and a flexible printed circuit (“FPC”) to provide a high transmission rate desirably has a resin composition having a low dielectric rate. However, because copper foil laminates which are generally used at present have a relatively large permitivity of about 4.5 to about 5.5, transmission loss and signal delay may be greater. Also, such board materials may hardly satisfy the specifications for next-generation packaging technology, such as excellent physical properties, high heat resistance, low thermal expansion, and low-moisture absorption. Therefore there remains a need for an improved board material that may provide such specifications.
Recently, researchers have been studying technologies which use a liquid crystal polymer resin, and particularly, a thermoplastic liquid crystal polymer (“LCP”) is regarded as an alternative material for a polyimide (“PI”), which is being used as a flexible copper foil laminate, which may be a rigid or flexible board material. This is because the liquid crystal polymer addresses many of the problems of the polyimide, which include high moisture absorption, dimensional instability, and large dielectric rate and dielectric loss values. Also, because a liquid crystal polymer resin has low dielectric rate and loss values even at a high frequency (“GHz”), it has excellent electrical characteristics.
A commercially available liquid crystal polymer has excellent electrical characteristics and a low coefficient of thermal expansion (“CTE”) due to low dielectric rate and loss values. Thus, researchers are studying use of the commercially available liquid crystal polymer as a rigid or flexible board material and an interlayer dielectric material. The commercially available liquid crystal polymer, however, has a drawback that it may be difficult to use as a flexible printed circuit (“FPC”) due to low stiffness and insufficient heat resistance, when the commercially available liquid crystal polymer is used alone. In the process of preparing a prepreg or laminating the prepreg with copper foil in order to fabricate a flexible printed circuit (“FPC”) using a liquid crystal polymer, a fusible LCP has lower workability, and a soluble LCP has a low glass transition temperature (“Tg”), a high processing temperature, and high viscosity of solid components, and thus the soluble LCP has a poor impregnation property and poor wettability on the surface of copper foil. Thus there remains a need for a soluble LCP having improved adhesion properties.